I am watching an area of severe weather potential across the Great Lakes region, particularly over parts of the Northeast into the upper Western Great Lakes. Also of concern is the threat of overnight thunderstorms across the darker red region.
In the early hours of tomorrow, the 18z NAM model is projecting a cluster of showers and thunderstorms to develop across northern Minnesota and shift eastward in the midst of little instability but modest lifting. Of particular concern to this potential cluster will be how it reacts to what is forecast to be a strong cap over the region. It is a given that the lower level jet stream is nocturnal, and this is likely what will enhance storms to form over the area and keep them going in what would otherwise be an unfavorable environment for thunderstorms.
At this point, we are approaching late morning and the mesoscale convective system continues to show signs of continuing to move across the upper Midwest region, at this point now into far northern Wisconsin and the northern portion of Michigan. The NAM is progging the lower level jet stream to be in the 50-55 knot vicinity, enough to support strong to severe thunderstorms, even in the nighttime or late morning hours, when instability is traditionally not strong. I feel that the Lower Great Lakes may have to be on watch in this time as well, as the NAM is indicating a good 25-35 knot streak in the lower level jet may come to a point in the region.
Moving on into the wee hours of Thursday morning, the MCS makes an attempt to enter the Northeast, now once again holding its strength to the tune of possibly 60 knots of wind in the lower level jet stream. 3 hour precip forecasts, as shown above, are not as significant as they were on Wednesday morning's forecast, but remain significant enough to pose the question of severe weather potential. Notice the hints of blue in the western portions of the Lower Great Lakes. Further analysis of the 700mb winds does show over 30 knots of winds over that region, which would support some showers and storms, but not exactly on a severe level.
Here is the 1 hour precipitation forecast off the 21z Rapid Refresh model. It shows the bulk of the precipitation placed north of where the NAM is showing. This, in turn, would lead to a severe weather risk displaced farther to the north, should the low pressure system responsible make a move for this solution. This image is valid at about 9:00 AM CDT tomorrow and is long range for this short range model. However, it is indeed worth watching and will need closer monitoring into the morning hours tomorrow.